Patent GB-1315247-A (GB)
Title: Separation colour recorder system
IPC: G03B27/475
Filed: 1971-04-19
Abstract: 1315247 Photographic colour printers MINNESOTA MINING & MFG CO 19 April 1971 [11 Feb 1970, 4 Sept 1970] 21576/71 Heading G2A [Also in Division H4] A colour film is produced from a colour television signal by (a) deriving a field sequential colour signal from the television signal and recording the successive field signals in successive frames on a mono-chromatic film, and (b) exposing each frame of a colour film to a group of frames of the mono-chromatic film using appropriately coloured light, each group including one frame pertaining to each colour signal e.g. red, green and blue. The colour television signal may comprise a composite signal or the simultaneous red, green and blue output signals from for example a television camera. In the case of a composite signal it is decoded into the red (R), green (G) and blue (B) signals, and passed via a matix or masking amplifier and gamma amplifiers (which mix and nonlinearly amplify the signals so that they are correct for the characteristics of the colour film) to a field sequencer which derives field sequential signals in repeating groups comprising RGBRG for a 60 field per second signal or RGBG for a 50 field per second signal or GRB for a 60 or 50 field per second signals. These signals are then recorded on a mono-chrome fine-grained film using an electron beam recorder, the film being continuously moved to establish the vertical scan. A colour film having a frame rate of 24 frames per second is produced from the mono-chromatic film having repeating groups of RGBRG frames recorded thereon by exposing successive frames to the first three frames (RGB) and the last three frames (BRG) of each group. The apparatus for effecting this exposure comprises a continuously rotating colour filter 108 having filter segments in the sequency RGBBRG, and a continuously rotating shutter 110 having six clear and six opaque segments, so arranged that each frame of the mono-chromatic film 36 (intermittently moved) is exposed by the appropriate light on to the intermittently moving colour film 100, each frame of which is exposed three times i.e. to R, G and B frames of the mono-chromatic film. Video signals having a 50 fields per second rate and recorded in the repeating groups RGBG on the mono-chrome film are usedby exposing a frame of the colour film to the first three frames RGB of a group and the next adjacent frame to the last two frames BG of the group and the first frame R of the next group. In this manner a colour film having 25 frames/sec is produced, the slight deviation from 24 frames/sec being undetectable by the human eye. Video signals having a 60 (or 50) fields per second rate and recorded in the repeating groups GRB i.e. 20 (or 16 2/3) groups per second, are converted into 24 (or 25) colour film frames per second by using every fifth group to print two colour frames (or every other group to print two colour frames). To reduce colour fringing it is desirable to use colour components for each colour frame which are from the same field of the video information. This may be effected by using a magnetic disc recording and reproducing system before the field sequencer in the monochrome film recording system to effect delays of one and two field periods for the red and blue field signals. To effect correct interlacing a half line period delay is also included in the red field playback channel from the magnetic disc recorder, or the recording beam of the electron beam recorder is alternately deflected in the vertical direction. To reduce irregularities in the motion due to particular colour groups being printed twice on the colour film, the following alternative arrangements may be utilized: (a) one out of every four colour video fields (60 per sec) is used to produce a colour group on the mono-chrome film (one and two field delays being used) each group comprising GRB frames and a blank (or duplicate colour frame), and this 15 colour groups per second mono-chrome film is converted into 24 colour frames per second by using the second, third and fifth groups out of every five groups to print two colour frames: (b) a mono-chrome film is recorded at 16 colour groups GRB per second from a 60 fields per second signal, a blank or duplicate frame being recorded after every colour group with the exception of a first colour group in every set of four colour groups, and every other group is used twice to produce a colour film at 24 frames per second: (c) a monochrome film is recorded at 18 colour groups GRB per second from a 60 fields per second signal, ablank or duplicate frame being recorded after every three groups, and each set of three groups is used to produce four colour frames: and (d) a mono-chrome film at 12 colour groups RGBGR per second is recorded from a 60 fields per second signal, and each group is used to produce two colour frames (the first R and G frames in each group are derived from one field, the B frame from the next field using a one field delay, and the second G and R frames from the third field using one and two field delays respectively).